Transfusion is a common mode of clinical therapy, and an estimated 12 million units of blood per year are collected in the United States. Progress in the collection, storage and testing of human blood has improved the lives of many patients, however many questions remain regarding transfusion biology and medicine. It is the purpose of this SCOR program to address some of these questions with a group of interrelated, collaborative projects. The areas of emphases are cytokines, red blood cell transfusion, and immunomodulatory aspects of transfusion. In the area of cytokines. Project I proposes clinical studies of the newly available cytokine, recombinant thrombopoietin, to pave the way for future therapeutic use of this cytokine to stimulate endogenous platelet production in thrombocytopenic patients. In basic studies which may lead to future therapeutic cytokines, Project 2 proposes a mouse model to study cytokine signalling in megakaryocytopoiesis, and Project 3 proposes gene- knockout mice to study the role of tyrosine kinases in cytokine signalling in hematopoiesis. In the area of red blood cell transfusion. Project 4 proposes clinical studies to monitor tissue perfusion and oxygenation which may guide fluid and red blood cell transfusion, therapy in adult surgical patients. Project 5 proposes studies of autologous placental red blood cell for transfusion to anther very important group of transfusion recipients, i.e. premature infants. In the area of immunomodulatory aspects of transfusion. Project 6 proposes dissecting the mechanism(s) of activation/proliferation of allogeneic donor leukocytes, cells which have been implicated in many adverse reactions to transfusion. Finally, Project 7 proposes basis investigation into the mechanisms of development of B cells, cells which make antibodies implicated in many adverse transfusion reactions. To support these projects are an administrative core and a biostatistical core. In developing the above Transfusion Biology and Medicine SCORE program, UCSF has formed a new, enthusiastic, and multidisciplinary team, taking advantage of its many Departments, including Anesthesia, Surgery, Pediatrics, Medicine, Immunology, and Transfusion Medicine.